The present invention relates to plastic preforms for preparing plastic containers especially for retention of fluids, as for carbonated beverages or the like. These containers may be prepared from a preform which may be injection or extrusion molded, followed by blow molding the preform into a suitably shaped container using a blow mold having the desired shape. Typical thermoplastic materials are polyethylene terephthalate (PET), polyolefins, etc., although others can be used.
The container and preform from which it is prepared generally includes a neck portion with a cap retaining means, a shoulder portion depending therefrom, a side wall or main body portion depending from the shoulder portion and a bottom portion joined to the side wall and depending therefrom. In many of these containers the bottom portion desirably has a champagne bottle bottom configuration with an axially, inwardly directed generally conical part.
In addition, the public prefers large size containers especially for the convenience and economy they represent, as, for example, the two liter containers widely used for carbonated beverages. Indeed, even larger containers would be desirable. However, these containers are awkward to handle, especially for small children. In addition, the walls of these containers tend to bulge, making them even more awkward to handle.
These bottles are made of different plastics, e.g., milk bottles are polyethylene (PE), still-water bottles often polyvinylchloride (PVC), and bottles for carbonated beverages are PET.
U.S. Pat. No. 5,242,066 describes a blow molded plastic bottle having neck, a side wall and a base, and including an internal member termed a spider attached to the side wall of the bottle which is said to increase the strength of the bottle. The bottle is formed from an injection molded preform, an integral portion of which the said spider is a part. A blown bottle is then made containing several compartments separated by the spider, which may also reinforce the side wall.
In order to facilitate handling large containers, handles or handgrips, are made in various ways, depending primarily on the material of the bottle and the process best suited to convert it into the desired shape. Thus, PE bottles are made by extrusion blow molding, a process in which a hollow handle may be made by action of the same mold that shapes the extruded preform into the bottle itself, as is well known. The prerequisites for this technique are an extruded preform and a plastic, such as PE, that may be readily pressure welded. Bottles made of PET from injection molded preforms do not have hollow, integral handles, because it is well-nigh impossible to weld PET into a closed handle by the above technique.
The art shows ways to provide handles for PET bottles, but none of them are integral with the body of the bottle, i.e., made from the preform used to blow the bottle itself. Instead, separately made handles are mechanically attached, or molded onto the finished body in a separate molding step, e.g., as shown in U.S. Pat. No. 4,727,997 to Y. Nakamura. This is an expensive and often unreliable procedure that is commercially unsuccessful.
A handgrip may be used as a substitute for a handle, the difference between the two being that, in grasping a handle, at least one finger of the user's hand is inserted into a hole formed by a loop attached to the bottle, or integral therewith while the handgrip, or simply grip, is formed by indentations in the bottle wall designed to permit grasping the grip between the thumb and forefingers.
Such a grip may be readily produced as an integral part of the bottle from an otherwise normal preform in a mold that has a corresponding cavity as part of the one forming the rest of the bottle wall. PET bottles with such a grip are used commercially, as for example to package spirits, wine and other liquids in large sizes, usually over 2 liters.
The same design cannot be used for bottles subjected to internal pressure, as in the case of carbonated beverages. It is well known that in a thin-walled, elastic, cylindrical body subject to internal pressure any indentation will bulge out and the body will assume a substantially circular cross-section in place of indentations that may have been present before pressure was applied.
One purpose of this invention is to provide an improved preform and an economical and aesthetically pleasing bottle made therefrom, which bottle may have a grip as part of its side-wall and which has an internal, integral reinforcing member to divide the container, to reinforce its walls, and to preclude everting under internal pressure, as the case may be.
Accordingly, it is a principal object of the present invention to provide an improved plastic preform, an improved blow molded plastic container and an improved method for preparing same.
It is a further object of the present invention to provide improvements as aforesaid which are inexpensive to obtain and are expeditious to provide on a commercial scale.
Further objects and advantages of the present invention will appear hereinbelow.